Governing Structural Code in 1923 in Portland Oregon

[msquared48]

Anyone have any idea what the governing structural code would have been in Portland, Oregon, in 1923?

We have an old R/C building with concrete moment frames we have to analyze and want to implement the 10% rule if possible, but we need to determine what lateral and vertical design forces may have been used at that time.

I am old, but not that old...

Mike McCann, PE, SE (WA)

 

[wannabeSE]

Since the first UBC was published in 1927, there may be no code or the city had there own. My only suggestion is to look at the wind loads in the 1923 and 1934 Carnegie Pocket Companion on SlideRuleEra's website. The 1934 edition (pdf page 358-359) list wind loads for various city building codes. They range from 15-30 psf. Portland would have been very progressive if they adopted any seismic code in 1923. If I can find it, I will post a brief history of building codes I read (focused on San Francisco bay area, I thought it was on Computer and Structures website but I can't find it).

However, knowing original design criteria should not be required to implement the 10% exceptions. It is just a % increase in demand or decrease in capacity. For instance, if a shear walls capacity is not reduced by 10% with a new opening when compared to the original construction is OK. Or, if the seismic mass/force contributing the load on the element in question is not increased by more than 10%, it is OK.

 

[racookpe1978]

But that would have 12 - 14 years after the 1906 San Francisco earthquake just "down the pike". Would not Portland have been one of the first cities to implement a structural code for new buildings started after the 1906-1910 period?

 

[SrVaro]

Maybe the 1915 National Building Code. The version I have is updated to be 1924. This is the oldest I have been able to find, it could get you close. It was the best I could find for a similar situation for modifications to an old 4-story Model-A factory that was R-C design. The code can be reviewed on-line from the University of Michigan library that is part of the Hathi Trust.

 

[hawkaz]

Call Shelly at the City of Portland Bureau of Development Services 503-823-7536. She is very helpful.